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01/07/2013

Preventing Foundation Settlement with Piers, Piles and Caissons

By Shawn Kyles

After a home has been built, weather conditions, soil issues and moisture problems can cause the foundation to settle. Foundation settlement can result in wall cracks, difficulties opening and closing windows and sloping floors. Over time, foundation settlement can compromise the structural integrity of the home. If you live in an area with extensive seismic activity, foundation settlement can be extremely dangerous and may even result in the home’s collapse during or after an earthquake.

To prevent settlement, some home foundations need to be shored up with piers, piles and caissons. Piers are steel pipes driven into the soil and connected to the foundation. They can be installed after a home is built with portable equipment and no significant disruption to the dwelling’s inhabitants. The piers are often connected with concrete beams.

Foundation piles include bearing piles and sheet piles. Bearing piles are used to absorb the weight of structure. Sheet piles block soil and water. Piles can be built using wood, concrete and composite materials. They are drilled into the ground using a pile driver. Helical piles are also commonly used in foundation repair. A helical pile is a straight piece of pipe welded with flights (steel plates). The helical flights enable the pipe to be literally screwed into the ground. Piles are connected with cement blocks, also known as pile caps, as well as grade beams.

Caissons are a third type of deep foundation used when soil conditions are extremely poor or the structure involved is large and heavy. Many hillside homes, apartment buildings and high-rise complexes require caissons to provide additional support. Caissons are also used when constructing bridges and freeways, as well as retaining walls designed to stabilize falling hillsides. When a hillside retaining wall is built, the soil behind it will exert pressure on the wall. This can cause the wall to fall, either by overturning, sliding or collapse.

Caissons are built by drilling a large, subterranean shaft. The shaft is then filled with reinforced concrete, along with steel or rebar. The shafts are drilled from 2’ to 12’ in diameter through the soil and into the bedrock. Some shafts are as deep as 150 feet.

If you are having foundation settlement problems, you can find out what type of shoring or strengthening is needed by consulting a foundation repair expert. Once your home and foundation has been properly inspected by a seasoned professional, all of your options will be explained so that you can make the best decision possible regarding your home.